It is known, in particular from French patent application No. 90 03279 in the name of the present Applicants, to provide a distributor box, or distribution housing, of a type which includes an air inlet arranged to admit a stream of cold air and/or a stream of heated air, together with a plurality of air outlets which are open towards various different zones within the cabin of the vehicle. These outlets comprise, in particular, a de-icing air outlet port which is open towards the windshield of the vehicle. The distributor box also contains a distributor valve which is mounted for pivoting movement about an axis inside the distributor box, for adjusting the distribution of the air between the various air outlets.
The air inlet of the distributor box is connected to the outlet of a heater housing which is adapted for producing a stream of cold air and a stream of hot air in adjustable proportions, according to the particular conditions required by the user.
Except in the extreme settings of the distributor valve, in which either only a stream of cold air or only a stream of heated air is produced, i.e. in intermediate positions of the valve, these two air streams generally leave the heater housing in the form of adjacent or stratified streams, so as to obtain what is referred to as temperature stratification. The two air streams are then introduced into the distributor box, in which they may again become mixed in proportions which are variable according to the zone or zones of the cabin to which they are to be directed.
Conventionally, apart from the de-icing air outlet which is open towards the windshield, the distributor box also has at least one ventilating air outlet which is open at the level of the fascia of the vehicle, together with at least one lower air inlet which is open into the lower part of the cabin, that is to say in such a way as to direct air towards the feet of the occupants of the vehicle.
The distributor valve may in particular be put into a "de-icing" position in which a stream of air is delivered towards the windshield, and a position which may be referred to as its "de-icing and foot warming" position, in which a stream of air is delivered simultaneously towards the windshield and towards the feet of the occupants of the vehicle. In these two positions, the stream of cold air and the stream of heated air delivered towards the windshield have a tendency to mix, so that the temperature of the air, thus mixed, is lower than the temperature of the heated air stream, thus having reduced effectiveness for deicing and de-misting the windshield.